Individual sensors and sensor networks are being used to an ever greater extent in a wide variety of applications to monitor ambient and operating conditions of systems. Such applications include, for example, building control systems for lighting, access control, climate control, and temperature regulation; industrial applications, such as monitoring power usage and distribution, environmental monitoring of air and water quality, chemical concentration, etc. Sensors are also being used in health care applications to monitor heart rate, blood pressure and other health status data.
There are several technical challenges associated with the use of sensors in this context. Generally, measurement data must be collected, processed and aggregated in a form adapted for transmission, and then transmitted to a controller and/or processing center either over a wireline or a wireless connection. Wired systems suffer the disadvantages that they are expensive to install, difficult to modify, limited in functionality once installed, and obtrusive with respect to preexisting infrastructure. Wireless systems overcome these difficulties since they are easy to install and modify, and do not necessarily interfere with any preexisting infrastructure. However, whereas a wired system has a well-defined connection between the sensor(s) and the base station, in wireless systems the connection between the sensor modules and the base station needs to be initialized, continually controlled and secured against breach, interception and hacking. In particular, during the initialization of the network, sensor network nodes, which receive signals directly from the sensors, must be validated before being admitted to the network.
Currently, there are two main techniques for controlling a wireless sensor network: i) providing an extensive user interface at the base station; and ii) using open networks to remotely control the wireless system. The former technique suffers from the fact that providing an extensive interface at the base station increases the complexity of the base station, requiring user interface controls and additional computing power. The latter “remote control” approach, which may be implemented using either PSTN (Public Service Telephone Network) or Internet-based connection in conjunction with a communications device at the wireless network base station, provides the advantage of worldwide remote access. As an example, U.S. Pat. No. 6,643,779 to Leung et al. describes a system in which the base station includes a web server functionality, thereby enabling communication between a local security network and the Internet. However, this technique suffers from the disadvantages that additional computational resources are required at the base station to implement the web server, Internet access must be static, and that the system remains exposed to hacking threats.